Terminale Spécialité Physique/chimie : Liste des chapitres
Chap09 : Évolution spontanée d'un système chimique
Exercices
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9.Eac2 : Écrire un quotient de réaction

Donner l’expression du quotient de réaction des réactions suivantes :

\(\ce{CH3COOH(aq) + H2O ⇄ CH3COO–(aq) + H3O+(aq)}\)

\(\ce{Cu(s) + 2 Ag+(aq) ⇄ Cu^2+(aq) + 2 Ag(s)}\)

\(\ce{3 I2 (aq) + 2 Al (s) ⇄ 6 I–(aq) + 2 Al3+(aq)}\)

\(\ce{H2O2 (aq) + 2 I–(aq) + 2 H+(aq) ⇄ I2 (aq) + 2H2O(l)}\)

Afficher la correction

\(K = \dfrac{\left(\dfrac{[\ce{H3O+}]}{c^0}\right)^1 × \left(\dfrac{[\ce{CH3COO-}]}{c^0}\right)^1}{\left(\dfrac{[\ce{CH3COOH}]}{c^0}\right)^1 × 1^1}\)

En \(\pu{mol*L-1}\) on obtient \(K = \dfrac{[\ce{H3O+}] × [\ce{CH3COO-}]}{[\ce{CH3COOH}]}\)

\(K = \dfrac{\left(\dfrac{[\ce{Cu^2+}]}{c^0}\right)^1 × 1^2}{1^1 × \left(\dfrac{[\ce{Ag+}]}{c^0}\right)^2}\)

En \(\pu{mol*L-1}\) on obtient \(K = \dfrac{[\ce{Cu^2+}]}{[\ce{Ag+}]^2}\)

\(K = \dfrac{\left(\dfrac{[\ce{I-}]}{c^0}\right)^6 × \left(\dfrac{[\ce{Al^3+}]}{c^0}\right)^2}{\left(\dfrac{[\ce{I2}]}{c^0}\right)^3 × 1^2}\)

En \(\pu{mol*L-1}\) on obtient \(K = \dfrac{[\ce{I-}]^6 × [\ce{Al^3+}]^2}{[\ce{I2}]^3}\)

\(K = \dfrac{\left(\dfrac{[\ce{I2}]}{c^0}\right)^1 × 1^2}{\left(\dfrac{[\ce{H2O2}]}{c^0}\right)^1 × \left(\dfrac{[\ce{I-}]}{c^0}\right)^2 × \left(\dfrac{[\ce{H+}]}{c^0}\right)^2}\)

En \(\pu{mol*L-1}\) on obtient \(K = \dfrac{[\ce{I2}]}{[\ce{H2O2}] × [\ce{I-}]^2 × [\ce{H+}]^2}\)